This invention broadly relates to a method and a device for removing an unnecessary film formed on a part of a surface of a substrate, such as a photo mask blank including a phase shift mask blank, a semiconductor substrate, a magnetic disk substrate, and a color filter, as well as to a method of manufacturing a photo mask blank.
In the field of manufacturing semiconductor devices, photo masks including phase shift masks, magnetic disk substrates, and color filters, it is often required to remove an unnecessary portion of a coating film or various other films formed on a surface of a substrate, which may shortly be referred to as a substrate surface.
For example, a resist or a SOG (spin on glass) film is formed on the substrate by the use of a spin coating method. In the spin coating method, the substrate is held in a substantially horizontal position and rotated while a coating fluid is dropped on the substrate to thereby form a uniform coating film on the substrate utilizing the centrifugal force.
In this case, if the substrate is rotated at a low speed such that the coating film is uniformly formed throughout the entire surface, the centrifugal force acting upon a peripheral region of the substrate surface becomes small. As a consequence, the coating fluid stays or remains in the peripheral region of the substrate surface so that the coating film is increased in thickness in the peripheral region. In other words, the coating film has a thickened or protruding portion in the peripheral region of the substrate surface.
When the coating film is thickened or protruded in the peripheral region of the substrate surface as mentioned above, various disadvantages will arise. For example, if the coating fluid is SOG, i.e., the coating film is the SOG film, cracks tend to be formed in the peripheral region. Further, in case where a phase shift mask with the SOG film formed on the substrate surface is attached to an exposure device, the substrate is often supported or fixed in the peripheral region. However, in case where the SOG film is protruded in the peripheral region of the substrate as mentioned above, good and reliable support can not be achieved.
Consideration will be made of the case where the coating fluid is a resist, i.e., the coating film is the resist film. For example, in order to perform contact exposure, a photo mask is superposed on the substrate with the resist film applied thereto. In this event, if the resist film is protruded in the peripheral region of the substrate as mentioned above, good and reliable contact between the photo mask and the resist film can not be achieved.
Meanwhile, a storage case is often used when the photo mask blank (including the phase shift mask blank) with the resist film is shipped. Further, a storage cassette may be used when the photo mask blank is produced.
Under such circumstances, the resist film protruding in the peripheral region or on the end face of the substrate surface may be detached in the cause of the storage case, the storage cassette, or the handling process of the photo mask blank, resulting in occurrence of dust. Thus, various disadvantages are caused during the production process of the photo mask.
Under the circumstances, it is necessary to remove, as an unnecessary portion of the coating film, the protruding portion formed in the peripheral region of the substrate surface. Such an unnecessary portion of the coating film may be referred to as an unnecessary film.
In order to remove the unnecessary film, various methods are proposed, for example, in Japanese Examined Patent Publication (B) No. S58-19350, Japanese Unexamined Patent Publication (A) No. H6-262124, and Japanese Unexamined Patent Publication (A) H7-20623.
In the method disclosed in Japanese Examined Patent Publication (B) No. S58-19350, a substrate is placed on a turntable with its principal surface facing upward and rotated while a solvent is sprayed from a nozzle arranged below. Alternatively, a cover having a hollow pyramidal shape is placed on the substrate surface and the solvent is supplied from the top of the pyramid to the peripheral region.
In the method disclosed in Japanese Unexamined Patent Publication (A) No. H6-262124, a predetermined gap is kept between a gap forming member and the substrate surface in a processing area where a processing liquid is to be supplied. Thus, the processing fluid is reliably introduced into the processing area.
In the method disclosed in Japanese Unexamined Patent Publication (A) No. H7-20623, gas is supplied through a gas introduction port formed in a cover member so as to prevent the solvent from leaking into the center of the substrate.
In case where the coating film formed on the substrate surface is the resist film, exposure sensitivity may be delicately influenced by thermal hysteresis applied to the resist, depending upon the material of the resist film. In such a resist film, exposure sensitivity will be nonuniform if the thermal hysteresis is different depending upon the location in the resist film.
Therefore, in case where the above-mentioned removal of the unnecessary film is carried out in an environment such that temperature distribution occurs in the resist film under the influence of the heat of evaporation of the solvent, exposure sensitivity of the resist film becomes nonuniform. However, none of the existing methods described above have addressed to such problem.
It is therefore an object of this invention to provide a method and a device for removing an unnecessary film or an unnecessary portion of a coating film formed on a substrate surface, which are capable of reliably removing the unnecessary film without producing temperature distribution in the coating film during a removing process to adversely affect the coating film and to provide a method of manufacturing a photo mask blank, which uses the above-mentioned removing method.
According to a first aspect of this invention, there is provided a method of removing, as an unnecessary film, an unnecessary portion of a coating film formed on a surface of a substrate as a substrate surface by dissolving the unnecessary film with a solvent, the method comprising the steps of:
covering the substrate surface with a cover member; and
supplying the solvent from the top of the cover member through a supply hole formed at a predetermined position of the cover member so that the unnecessary film is dissolved by the solvent and removed;
the cover member defining a gap between an inner surface thereof and the substrate surface, the substrate surface having an unprocessed region where the coating film is to be left as a necessary film and a processed region where the coating film is to be removed as the unnecessary film, the gap in the unprocessed region having a size such that temperature distribution is not caused in the coating film formed on the substrate surface under the influence of heat transfer from the cover member.
According to a second aspect of this invention, there is provided a method of removing, as an unnecessary film, an unnecessary portion of a coating film formed on a surface of a substrate as a substrate surface by dissolving the unnecessary film with a solvent, the method comprising the steps of:
covering the substrate surface with a cover member; and
supplying the solvent from the top of the cover member through a supply hole formed at a predetermined position of the cover member so that the unnecessary film is dissolved by the solvent and removed;
the cover member defining a gap between an inner surface thereof and the substrate surface, the substrate surface having an unprocessed region where the coating film is to be left as a necessary film and a processed region where the coating film is to be removed as the unnecessary film, the gap in the unprocessed region having a size such that temperature distribution is not caused in the coating film formed on the substrate surface under the influence of heat transfer from the cover member and that temperature distribution is not caused in the coating film formed on a principal surface of the substrate due to convection of gas produced in the gap.
According to a third aspect of this invention, there is provided the method in the first or the second aspect, wherein, in the unprocessed region of the substrate surface, the gap has a constant or fixed size.
According to a fourth aspect of this invention, there is provided the method in any one of the first through the third aspects, wherein, in the processed region of the substrate surface, the gap has a size selected so that the solvent supplied to the gap is allowed to pass through the gap and spread in the gap.
According to a fifth aspect of this invention, there is provided the method in any one of the first through the fourth aspects, wherein, in the processed region of the substrate surface, a string-like member having a predetermined thickness is interposed between the inner surface of the cover member and the substrate surface to serve as a gap defining member for defining the size of the gap between the inner surface of the cover member and the substrate surface.
According to a sixth aspect of this invention, there is provided the method in any one of the first through the fifth aspects, wherein the unnecessary film is dissolved and removed by the solvent supplied through the supply hole while the substrate and the cover member are rotated together.
According to a seventh aspect of this invention, there is provided the method in any one of the first through the sixth aspects, wherein the solvent is supplied from the top of the cover member and also supplied from a rear side of the substrate towards the processed region of the Substrate.
According to an eighth aspect of this invention, there is provided a device for removing, as an unnecessary film, an unnecessary portion of a coating film formed on a surface of a substrate as a substrate surface by dissolving the unnecessary film with a solvent, the device comprising:
a cover member covering the substrate surface; and
a solvent supply unit for supplying the solvent from the top of the cover member;
the cover member having a supply hole through which the solvent from the solvent supply unit is supplied to the unnecessary film to thereby dissolve and remove the unnecessary film;
the cover member defining a gap between an inner surface thereof and the substrate surface, the substrate surface having an unprocessed region where the coating film is to be left as a necessary film and a processed region where the coating film is to be removed as the unnecessary film, the gap in the unprocessed region having a size such that temperature distribution is not caused in the coating film formed on the substrate surface under the influence of heat transfer from the cover member and that temperature distribution is not caused in the coating film formed on the substrate surface due to convection of gas produced in the gap.
According to a ninth aspect of this invention, there is provided the device in the eighth aspect, wherein, in the unprocessed region of the substrate surface, the gap has a constant or fixed size.
According to a tenth aspect of this invention, there is provided the device in the eighth or the ninth aspect, wherein, in the processed region of the substrate surface, the gap has a size selected so that the solvent supplied to the gap is allowed to pass through the gap and spread in the gap.
According to an eleventh aspect of this invention, there is provided a method of manufacturing a photo mask blank, the method including a film forming process of forming on a light transmitting substrate a film having a light shielding function and/or a phase shift function and a resist film, wherein the film forming process includes an unnecessary film removing process of removing, as an unnecessary film, an unnecessary portion of the resist film by the method described in any one of the first through the seventh aspects.
Herein, it is to be noted that the film having the light shielding function and/or the phase shift function is preferably formed by the use of the known sputtering or vapor deposition while the resist film is desirably formed by the known coating method.
In the first aspect, in the unprocessed region of the substrate (including not only a principal surface but also side surfaces and a rear surface) where the coating film is to be left as the necessary film, the gap between the inner surface of the cover member and the substrate surface has a size selected so that temperature distribution is not caused in the coating film formed on the substrate surface under the influence of heat transfer from the cover member.
With this structure, the unnecessary film can be removed without producing temperature distribution which will be caused by heat transfer from the cover member during a removing process and which may adversely affect the coating film.
Even if the heat of evaporation of the solvent nonuniformly acts on the surface of the cover member to cause temperature distribution in the cover member, it is possible to prevent the coating film on the substrate surface from being influenced by the temperature distribution to become nonuniform in temperature. Therefore, even in case where the coating film is a resist film whose sensitivity may become nonuniform if the thermal hysteresis is different depending upon the location in the resist film, it is possible to effectively prevent the occurrence of such nonuniform sensitivity.
Further, the cover member need not have a special arrangement for preventing the nonuniformity in temperature on its outer surface from reaching the inner surface.
In the second aspect, in the unprocessed region of the substrate where the coating film is to be left as the necessary film, the gap between the inner surface of the cover member and the substrate surface has a size selected so that temperature distribution is not caused in the coating film formed on the substrate surface under the influence of heat transfer from the cover member and that temperature distribution is not caused in the coating film formed on the principal surface of the substrate due to convection of gas produced in the gap.
With this structure, the unnecessary film can be removed, more effectively preventing the occurrence of temperature distribution which will be caused by heat transfer from the cover member during a removing process and which may adversely affect the coating film.
In the third aspect, in the unprocessed region of the substrate surface where the coating film is to be left as the necessary film, the gap between the inner surface of the cover member and the substrate surface has a constant or fixed size.
With this structure, the unnecessary film can be removed, more effectively preventing the occurrence of temperature distribution which will be caused by heat transfer from the cover member during a removing process and which may adversely affect the coating film.
In the fourth aspect, in the processed region of the substrate surface where the coating film is to be removed as the unnecessary film, the gap between the inner surface of the cover member and the substrate surface has a size selected so that the solvent supplied to the gap is allowed to pass through the gap and spread in the gap by the action of surface tension or the like.
With this structure, the solvent supplied from the solvent supply hole can reliably and accurately supplied to the unnecessary film to remove the unnecessary film. For example, the unnecessary film can be removed over a removing width corresponding to the width of a peripheral flat portion of the cover member.
In the fifth aspect, in the processed region of the substrate surface where the coating film is to be removed as the unnecessary film, the string-like member having a predetermined thickness is interposed between the inner surface of the cover member and the substrate surface to serve as a gap defining member for defining the size of the gap between the inner surface of the cover member and the substrate surface. With this structure, the gap having a predetermined size can very easily be formed without providing a special equipment for flowing the solvent throughout the gap in the processed region.
In the sixth aspect, the unnecessary film is dissolved and removed by the solvent supplied through the supply hole while the substrate and the cover member are rotated together. With this structure, the solvent can be uniformly spread and more easily and reliably supplied to the unnecessary film.
In the seventh aspect, the solvent is supplied from the top of the cover member and also supplied from the rear side of the substrate towards the processed region of the substrate where the coating film is to be removed as the unnecessary film. With this structure, the unnecessary film can be more reliably removed. It is noted here that the solvent may be supplied from the rear side prior to, simultaneously with, or subsequent to the supply from the top of the cover member. Alternatively, the solvent may be supplied from the rear side intermittently.
In the eighth aspect, it is possible to obtain a device capable of implementing the methods in the first and second aspects.
In the ninth aspect, in the unprocessed region of the substrate surface where the coating film is to be left as the necessary film, the gap between the inner surface of the cover member and the substrate surface has a constant or fixed size.
With this structure, the unnecessary film can be removed, more effectively preventing the occurrence of temperature distribution which will be caused by heat transfer from the cover member during a removing process and which may adversely affect the coating film.
In the tenth aspect, it is possible to obtain a device capable of more accurately removing the unnecessary film to be removed.
In the eleventh aspect, it is possible to obtain a method of manufacturing a photo mask blank, which is capable of accurately and more easily and reliably removing the unnecessary film.
Herein, xe2x80x9cthe film having a light shielding function and/or a phase shift functionxe2x80x9d mentioned above includes a film having a light shielding function, i.e., a light shielding film, a film having both a light shielding function and a phase shift function, i.e., a halftone film, and a film having a phase shift function, i.e., a phase shift film. The photo mask blank includes a conventional photo mask blank with a light shielding film alone formed thereon and a phase shift mask blank with a halftone film or a phase shift film formed thereon.